Kinetic and structural study of broccoli myrosinase and its interaction with different glucosinolates

Strategy for preparing of glucosinolate derivatives with outstanding functional activities based on myrosinase

Glucosinolates are a class of sulfur- and nitrogen-containing secondary metabolites that are widely present in cruciferous vegetables. Degradation products of glucosinolate, glucosinolate derivatives such as sulforaphane, sulforaphene, and iberin, have garnered interest due to their promising functional activities including anticancer, antioxidant, and antibacterial activities. As a result, these glucosinolate derivatives have substantial implications in the realms of food, medicine, and agriculture. Among the methods for preparing glucosinolate derivatives, enzymatic approach based on myrosinase stands out as a greener and more efficient alternative to chemical synthesis, underscoring the scientific and practical significance of developing myrosinase with high catalytic activity. This paper provides a systematic overview of the origin, catalytic properties, and catalytic mechanism of the key myrosinase applied for glucosinolate derivatives preparation. Meanwhile, the glucosinolate derivatives prepared via myrosinase and their functional activities are also illustrated and discussed. Furthermore, it also anticipates future research directions in myrosinase and glucosinolate derivatives.

Mining of Novel Myrosinase with High Activity Based on Sequence and Structure Clustering for Efficient Preparation of Sulforaphane

Sulforaphane has garnered significant research attention owing to its potent and promising biological activities. Mining the highly active myrosinase is the key to preparing sulforaphane. In this study, a novel myrosinase, designated Semyr, was identified from Serratia plymuthica through sequence and structural clustering analysis. The enzyme was heterologously expressed in Escherichia coli, demonstrating a sinigrin hydrolysis activity of 110.48 U/mg, which constitutes the highest recombinant myrosinase activity reported to date. A reaction system was established to prepare sulforaphane. 60 U of myrosinase was added to 5 mL of substrate, yielding 15.39 mg of sulforaphane per gram of broccoli seeds after 20 min at 40 °C and pH 6.0, with a conversion rate of 96.50%. Concurrently, the highest productivity of 5.55 μmol/g·min for sulforaphane was achieved after 15 min. Thus, Semyr serves as a valuable biocatalytic tool for the efficient preparation of sulforaphane.

Characterization of Myrosinase-Mediated Glucosinolate Degradation Pathways in Lactiplantibacillus plantarum ZUST49

Cruciferous vegetables are rich in glucosinolates that can be hydrolyzed by myrosinase into isothiocyanates (ITCs) with significant anticancer properties. In the absence of bacterial myrosinase, glucosinolates are excreted from the body in their inactive forms. However, the mechanisms underlying the bacterial breakdown of glucosinolates are not well understood. Here, we investigated the mechanism and enzymes involved in glucosinolate breakdown by the probiotic microorganism Lactiplantibacillus plantarum ZUST49, which degrades the glucosinolate glucoraphanin to sulforaphane and erucin. The glucoraphanin-degrading activity of this strain was induced by the presence of glucoraphanin and an absence of glucose. UPLC-MS analysis of the degradation products indicated that glucoraphanin was degraded via three distinct pathways, and further, transcriptomic and proteomic analyses led to the identification of a myrosinase gene, LpMyr, that encodes a 460-amino acid enzyme. The purified LpMyr protein exhibited optimal activity at 50 °C and pH 7.0, with hydrolysis rates of 7.74 U/mg for glucoraphanin and 5.89 U/mg for sinigrin. These findings provide new insights into the glucosinolate conversion capability of L. plantarum and highlight its potential for high-yield ITC production in the fermentation industry, as well as its potential use as a probiotic in the human gut.

Glucosinolates and Their Hydrolytic Products-A Love Story of Environmental, Biological, and Chemical Conditions

BACKGROUND

Glucosinolates (GSL) play an important role in providing defense to plants and helping them to cope with various biotic, as well as abiotic, stresses. Many living beings including humans and animals, including some herbivores, have adapted themselves to use this defense mechanism for their own use. More than 120 glucosinolates are distributed within a large number of plants. Many factors are known to influence the GSL composition in a plant. Among these, cofactors, myrosinase isozymes, heavy metals and the environmental conditions such as light, CO2 and temperature are important in regulation. These factors ensure that different glucosinolate compositions can be produced by the plants, thus impacting the defense mechanism.

OBJECTIVE

The objective of the current review is to highlight the importance of the factors responsible for affecting glucosinolate composition and concentration.

METHODS

The review has been compiled using accessible literature from Pubmed, Scopus, and Google scholar. Efforts have been made to restrict the literature to the last 5 years (2018-2023), with some exceptions.

RESULTS

The current critical review acts as a resource for all the researchers working on these essential compounds. It provides information on the factors that may influence glucosinolate production. It also gives them an opportunity to modify the glucosinolate composition of a plant using the given information.

CONCLUSIONS

Glucosinolates have long been an ignored class of biomolecule. The plethora of biological activities of the compounds can be useful. Though there are some harmful components such as goitrin and progoitrin, these can be easily removed by modulating some of the factors highlighted in the review.

HIGHLIGHTS

The current review has covered most of the factors that have the ability to modify glucosinolate composition and concentration. The mechanistic action of these factors has also been discussed using the current available literature.

The Effect of Broccoli Glucosinolates Hydrolysis Products on Botrytis cinerea: A Potential New Antifungal Agent

The present study investigates the interactions between eight glucosinolate hydrolysis products (GHPs) sourced from broccoli by-products and the detoxifying enzymes of Botrytis cinerea, namely eburicol 14-alpha-demethylase (CYP51) and glutathione-S-transferase (GST), through in silico analysis. Additionally, in vitro assays were conducted to explore the impact of these compounds on fungal growth. Our findings reveal that GHPs exhibit greater efficacy in inhibiting conidia germination compared to mycelium growth. Furthermore, the results demonstrate the antifungal activity of glucosinolate hydrolysis products derived from various parts of the broccoli plant, including inflorescences, leaves, and stems, against B. cinerea. Importantly, the results suggest that these hydrolysis products interact with the detoxifying enzymes of the fungus, potentially contributing to their antifungal properties. Extracts rich in GHPs, particularly iberin and indole-GHPs, derived from broccoli by-products emerge as promising candidates for biofungicidal applications, offering a sustainable and novel approach to plant protection by harnessing bioactive compounds from agricultural residues.

Engineering Brassica Crops to Optimize Delivery of Bioactive Products Postcooking

Glucosinolates are plant-specialized metabolites that can be hydrolyzed by glycosyl hydrolases, called myrosinases, creating a variety of hydrolysis products that benefit human health. While cruciferous vegetables are a rich source of glucosinolates, they are often cooked before consumption, limiting the conversion of glucosinolates to hydrolysis products due to the denaturation of myrosinases. Here we screen a panel of glycosyl hydrolases for high thermostability and engineer the Brassica crop, broccoli (Brassica oleracea L.), for the improved conversion of glucosinolates to chemopreventive hydrolysis products. Our transgenic broccoli lines enabled glucosinolate hydrolysis to occur at higher cooking temperatures, 20 °C higher than in wild-type broccoli. The process of cooking fundamentally transforms the bioavailability of many health-relevant bioactive compounds in our diet. Our findings demonstrate the promise of leveraging genetic engineering to tailor crops with novel traits that cannot be achieved through conventional breeding and improve the nutritional properties of the plants we consume.

Genotypes of Eruca vesicaria subsp. sativa grown in contrasting field environments differ on transcriptomic and metabolomic levels, significantly impacting nutritional quality

Rocket (Eruca vesicaria subsp. sativa) is a source of sulfur-containing glucosinolates (GSLs). GSLs and their breakdown hydrolysis products (GHPs) are responsible for health-related benefits, such as anti-cancer and anti-neurodegenerative properties. Understanding how phytochemical composition changes between cultivation environments is key to developing cultivars with improved nutritional quality. Two consecutive harvests (first and second regrowth) of crops, grown in both Italy and the UK, were used to determine the phytochemical and transcriptomic differences between six lines of Eruca. Samples were taken upon delivery from field sites (D0) and after five days of cold storage (D5) for each location. Leaves were analysed for sulfur content, volatile organic compounds (VOCs), GSLs, GHPs, and sugars. Transcriptome data were associated with metabolite profiles to identify differentially expressed genes between plants grown in the two environments. VOC compounds (carbon disulfide, methyl thiocyanate) were associated with growth environment and with differences in sulfur metabolism gene expression (APR2, LSU2, LSU3, SDI1, SiR), GSL biosynthesis (MYB28, FMOGS-OX2) and GHP formation (ESM1, TGG1, TGG2). The concentrations of sugars were an order of magnitude greater in UK grown samples (up to 29.9 mg g-1 dry weight; dw). Sulfur content was significantly higher in the Italy plant samples (11.4 - 20.1 mg g-1 dw), which was in turn associated with higher concentrations of GSLs (pentyl GSL, up to 15.8 μmol g-1 dw; sinigrin, up to 0.005 μmol g-1 dw; glucoraphanin, up to 5.1 μmol g-1 dw; glucorucolamine, up to 23.6 μmol g-1 dw; neoglucobrassicin, up to 5.3 μmol g-1 dw) and hydrolysis products (sativin, up to 13.5 μmol g-1 dw; erucin, up to 1 μmol g-1 dw; sulforaphane, up to 34.7 μmol g-1 dw). VOC profiles of plants cultivated in the UK were distinct from Italy grown plants, with higher relative abundances of alkanes and esters in second cut and shelf-life (D5) samples. The data indicate a significant interaction of cultivar response with environment, highlighting the difficulty of producing Eruca crops with consistent phytochemical and postharvest traits. Genes with differential expression between plants grown in Italy and the UK could be used as markers of phytochemical quality and composition.

Anticancer activity of broccoli, its organosulfur and polyphenolic compounds

The use of natural bioactive constituents from various food sources for anticancer purposes has become increasingly popular worldwide. Broccoli (Brassica oleracea var. italica) is on the top of the consumed vegetables by the masses. Its raw matrix contains a plethora of phytochemicals, such as glucosinolates and phenolic compounds, along with rich amounts of vitamins, and minerals. Consumption of broccoli-derived phytochemicals provides strong antioxidant effects, particularly due to its sulforaphane content, while modulating numerous molecules involved in cell cycle regulation, control of apoptosis, and tuning enzyme activity. Thus, the inclusion of broccoli in the daily diet lowers the susceptibility to developing cancers. Numerous studies have underlined the undisputable role of broccoli in the diet as a chemopreventive raw food, owing to the content in sulforaphane, an isothiocyanate produced as a result of hydrolysis of precursor glucosinolates called glucoraphanin. This review will provide evidence supporting the specific role of fresh florets and sprouts of broccoli and its key bioactive constituents in the prevention and treatment of different cancers; a number of studies carried out in the in vitro and in vivo conditions as well as clinical trials were analyzed.

Microorganisms-An Effective Tool to Intensify the Utilization of Sulforaphane

Sulforaphane (SFN) was generated by the hydrolysis of glucoraphanin under the action of myrosinase. However, due to the instability of SFN, the bioavailability of SFN was limited. Meanwhile, the gut flora obtained the ability to synthesize myrosinase and glucoraphanin, which could be converted into SFN in the intestine. However, the ability of microorganisms to synthesize myrosinase in the gut was limited. Therefore, microorganisms with myrosinase synthesis ability need to be supplemented. With the development of research, microorganisms with high levels of myrosinase synthesis could be obtained by artificial selection and gene modification. Researchers found the SFN production rate of the transformed microorganisms could be significantly improved. However, despite applying transformation technology and regulating nutrients to microorganisms, it still could not provide the best efficiency during generating SFN and could not accomplish colonization in the intestine. Due to the great effect of microencapsulation on improving the colonization ability of microorganisms, microencapsulation is currently an important way to deliver microorganisms into the gut. This article mainly analyzed the possibility of obtaining SFN-producing microorganisms through gene modification and delivering them to the gut via microencapsulation to improve the utilization rate of SFN. It could provide a theoretical basis for expanding the application scope of SFN.

Potential of Sulforaphane and Broccoli Membrane Vesicles as Regulators of M1/M2 Human Macrophage Activity

Macrophages have emerged as important therapeutic targets in many human diseases. The aim of this study was to analyze the effect of broccoli membrane vesicles and sulphoraphane (SFN), either free or encapsulated, on the activity of human monocyte-derived M1 and M2 macrophage primary culture. Our results show that exposure for 24 h to SFN 25 µM, free and encapsulated, induced a potent reduction on the activity of human M1 and M2 macrophages, downregulating proinflammatory and anti-inflammatory cytokines and phagocytic capability on C. albicans. The broccoli membrane vesicles do not represent inert nanocarriers, as they have low amounts of bioactive compounds, being able to modulate the cytokine production, depending on the inflammatory state of the cells. They could induce opposite effects to that of higher doses of SFN, reflecting its hormetic effect. These data reinforce the potential use of broccoli compounds as therapeutic agents not only for inflammatory diseases, but they also open new clinical possibilities for applications in other diseases related to immunodeficiency, autoimmunity, or in cancer therapy. Considering the variability of their biological effects in different scenarios, a proper therapeutic strategy with Brassica bioactive compounds should be designed for each pathology.

Development of a "Turn off-on" whole-cell biosensor for sulforaphane detection based on the ultrasensitive activator HrpRS

Sulforaphane (SFN), a defense secondary metabolite, can be used to predict the health status of plants and also has pharmacological effects, including anticancer, antioxidant, and anti-inflammatory properties. The detection of SFN is therefore of great significance for the prevention and treatment of diseases. In this study, a "Turn off" whole-cell biosensor that can rapidly and robustly respond to the presence of SFN was constructed based on the orthogonal genetic components (hrpR, hrpS, and P_hrpL ) of Pseudomonas syringae (PS). The final optimized biosensor, p114(30R-30S), was able to inhibit 91.7% of the fluorescence intensity in the presence of 100-μM SFN. Subsequently, a HrpRS-regulated OFF-ON genetic switch was designed by reconstituting a reverse σ⁷⁰ promoter on the σ⁵⁴ -P_hrpL promoter sequence; this was coupled with dual-color reporter genes to construct a "Turn off-on" whole-cell SFN biosensor. The P_hrpLB variant increased the expression of green fluorescence a factor of 11.9 and reduced the expression of red fluorescence by 85.8% compared with the system in the absence of SFN. Thus, a robust switching of signal output from "turn off" to "turn on" was realized. In addition, the biosensor showed good linearity in the SFN concentration ranges of 0.1-10 μM (R² = 0.99429) and 10-100 μM (R² = 0.99465) and a detection limit of ⁓0.1 μM. This article is protected by copyright. All rights reserved.

The glucosinolate profiles of Brassicaceae vegetables responded differently to quick-freezing and drying methods

Glucosinolates (GLS) are bioactive compounds found in Brassicaceae vegetables. Industrial food processing treatments, such as blanching, quick-freezing (QF), vacuum freeze-drying (VFD), vacuum-drying (VD) and oven-drying (OD), significantly affect the degradation and ingestion of GLS. Here, the effects of these treatments, followed by boiling, on the GLS content and mimicking ingestion level of isothiocyanate from Brassicaceae vegetables (broccoli, cauliflower, white and red cabbages, Chinese and baby cabbages, white and red radish roots) were investigated. The results showed that blanching-QF maintained or increased the GLS content as well as preserved the ingestion level of isothiocyanate, an optimum treatment for GLS preservation. Blanching-VFD was recommended for these vegetables, while blanching-VD and blanching-OD caused relatively high GLS losses and low isothiocyanate production. Additionally, stabilities of individual GLS during processing rely on their chemical structures and species. Generally, aliphatic GLS from Brassicaceae showed lower loss than indole GLS, indicating differences in their stabilities during processing.

Kinetic Study and Modeling of Wild-Type and Recombinant Broccoli Myrosinase Produced in E. coli and S. cerevisiae as a Function of Substrate Concentration, Temperature, and pH

The myrosinase enzyme hydrolyzes glucosinolates, among which is glucoraphanin, the precursor of the anticancer isothiocyanate sulforaphane (SFN). The main source of glucoraphanin is Brassicaceae; however, its natural concentration is relatively low, limiting the availability of SFN. An option to obtain SFN is its exogenous production, through enzymatic processes and under controlled conditions, allowing complete conversion of glucoraphanin to SFN. We characterized the kinetics of wild-type (BMYR) and recombinant broccoli myrosinases produced in E. coli (EMYR) and S. cerevisiae (SMYR) in terms of the reaction conditions. Kinetics was adjusted using empirical and mechanistic models that describe reaction rate as a function of substrate concentration, temperature, and pH, resulting in R2 values higher than 90%. EMYR kinetics differed significantly from those of BMYR and SMYR probably due to the absence of glycosylations in the enzyme produced in E. coli. BMYR and SMYR were subjected to substrate inhibition but followed different kinetic mechanisms attributed to different glycosylation patterns. EMYR (inactivation Ea = 76.1 kJ/mol) was more thermolabile than BMYR and SMYR. BMYR showed the highest thermostability (inactivation Ea = 52.8 kJ/mol). BMYR and EMYR showed similar behavior regarding pH, with similar pK1 (3.4 and 3.1, respectively) and pK2 (5.4 and 5.0, respectively), but differed considerably from SMYR.

Assessment of Methodological Pipelines for the Determination of Isothiocyanates Derived from Natural Sources

Isothiocyanates are biologically active secondary metabolites liberated via enzymatic hydrolysis of their sulfur enriched precursors, glucosinolates, upon tissue plant disruption. The importance of this class of compounds lies in their capacity to induce anti-cancer, anti-microbial, anti-inflammatory, neuroprotective, and other bioactive properties. As such, their isolation from natural sources is of utmost importance. In this review article, an extensive examination of the various parameters (hydrolysis, extraction, and quantification) affecting the isolation of isothiocyanates from naturally-derived sources is presented. Overall, the effective isolation/extraction and quantification of isothiocyanate is strongly associated with their chemical and physicochemical properties, such as polarity-solubility as well as thermal and acidic stability. Furthermore, the successful activation of myrosinase appears to be a major factor affecting the conversion of glucosinolates into active isothiocyanates.

Biochemical Characterization of a Novel Myrosinase Rmyr from Rahnella inusitata for High-Level Preparation of Sulforaphene and Sulforaphane

Myrosinase is a biotechnological tool for the preparation of sulforaphane and sulforaphene with a variety of excellent biological activities. In this study, a gene encoding the novel glycoside hydrolase family 3 (GH3) myrosinase Rmyr from Rahnella inusitata was heterologously expressed in Escherichia coli BL21 (DE3). The purified Rmyr shows the highest activity at 40 °C and pH 7.0; meanwhile, its half-life at 30 °C reaches 12 days, indicating its excellent stability. Its sinigrin-, glucoraphenin-, and glucoraphanin-hydrolyzing activities were 12.73, 4.81, and 6.99 U/mg, respectively. Rmyr could efficiently degrade the radish seed-derived glucoraphenin and the broccoli seed-derived glucoraphanin into sulforaphene and sulforaphane within 10 min with the highest yields of 5.07 mg/g radish seeds and 9.56 mg/g broccoli seeds, respectively. The highest conversion efficiencies of sulforaphane from glucoraphanin and sulforaphene from glucoraphenin reached up to 92.48 and 97.84%, respectively. Therefore, Rmyr is a promising and potent biocatalyst for efficient and large-scale preparation of sulforaphane and sulforaphene.

Membrane Vesicles for Nanoencapsulated Sulforaphane Increased Their Anti-Inflammatory Role on an In Vitro Human Macrophage Model

At present, there is a growing interest in finding new non-toxic anti-inflammatory drugs to treat inflammation, which is a key pathology in the development of several diseases with considerable mortality. Sulforaphane (SFN), a bioactive compound derived from Brassica plants, was shown to be promising due to its anti-inflammatory properties and great potential, though its actual clinical use is limited due to its poor stability and bioavailability. In this sense, the use of nanocarriers could solve stability-related problems. In the current study, sulforaphane loaded into membrane vesicles derived from broccoli plants was studied to determine the anti-inflammatory potential in a human-macrophage-like in vitro cell model under both normal and inflammatory conditions. On the one hand, the release of SFN from membrane vesicles was modeled in vitro, and two release phases were stabilized, one faster and the other slower due to the interaction between SFN and membrane proteins, such as aquaporins. Furthermore, the anti-inflammatory action of sulforaphane-loaded membrane vesicles was demonstrated, as a decrease in interleukins crucial for the development of inflammation, such as TNF-α, IL-1β and IL-6, was observed. Furthermore, these results also showed that membrane vesicles by themselves had anti-inflammatory properties, opening the possibility of new lines of research to study these vesicles, not only as carriers but also as active compounds.

Broccoli Myrosinase cDNA Expression in Escherichia coli and Saccharomyces cerevisiae

Myrosinases (EC 3.2.1.147) are enzymes known for the generation of hydrolysis products that have a potential beneficial effect on human health. Their reaction mechanisms are widely studied, in order to improve and optimize secondary metabolite production processes. In this work, kinetic and biochemical properties of the broccoli myrosinase enzyme produced from its cDNA cloned in Escherichia coli and Saccharomyces cerevisiae were investigated. The results revealed that the thermal stability of the enzyme produced in S. cerevisiae was slightly higher (30 to 60 °C) than that of myrosinase produced in E. coli (20 to 50 °C). The effect of pH on the enzymatic activity was similar in both enzymes, with pH 3 being the optimum value under the reaction conditions used. The kinetic behavior of both enzymes was adjusted to the Michaelis–Menten model. The catalytic efficiency was up to 4 times higher in myrosinase produced in S. cerevisiae, compared to myrosinase produced in E. coli. The glycosylations present in the enzyme would be related to the formation of a dimeric quaternary structure and would not play an essential role in enzymatic activity, since both enzymes were biologically active. These results will probably allow the development of strategies for the production of bioactive metabolites of medical interest.

A Physiological-Based Model for Simulating the Bioavailability and Kinetics of Sulforaphane from Broccoli Products

There are no known physiological-based digestion models that depict glucoraphanin (GR) to sulforaphane (SR) conversion and subsequent absorption. The aim of this research was to make a physiological-based digestion model that includes SR formation, both by endogenous myrosinase and gut bacterial enzymes, and to simulate the SR bioavailability. An 18-compartment model (mouth, two stomach, seven small intestine, seven large intestine, and blood compartments) describing transit, reactions and absorption was made. The model, consisting of differential equations, was fit to data from a human intervention study using Mathwork’s Simulink and Matlab software. SR urine metabolite data from participants who consumed different broccoli products were used to estimate several model parameters and validate the model. The products had high, medium, low, and zero myrosinase content. The model’s predicted values fit the experimental values very well. Parity plots showed that the predicted values closely matched experimental values for the high (r² = 0.95), and low (r² = 0.93) products, but less so for the medium (r² = 0.85) and zero (r² = 0.78) myrosinase products. This is the first physiological-based model to depict the unique bioconversion processes of bioactive SR from broccoli. This model represents a preliminary step in creating a predictive model for the biological effect of SR, which can be used in the growing field of personalized nutrition.

Transcriptome and metabolome profiling to elucidate mechanisms underlying the blue discoloration of radish roots during storage

The internal blue discoloration of radish roots (Raphanus sativus) during storage affects their quality. We here performed transcriptome and metabolome profiling to investigate the mechanisms underlying the bluing of radish roots during storage. On comparing white radish (WR) and blue radish (BR), we identified 14,171 differentially expressed genes (upregulated: 7,383, downregulated: 6,788) and 145 differentially accumulated metabolites (upregulated: 117, downregulated: 28). Functional annotation analysis and metabolome profiling revealed that the blue discoloration of radish roots was promoted by high content of glucosinolates, oxidation system (ROS, CAT, POD) or low reduction system (GSH, GPX, APX, GST, ASA). Our results provide new insights into the underlying metabolic causes of the blue discoloration of radish roots and report candidate genes and metabolites involved in blue compound biosynthesis.

Fine mapping of the major QTLs for biochemical variation of sulforaphane in broccoli florets using a DH population

Glucoraphanin is a major secondary metabolite found in Brassicaceae vegetables, especially broccoli, and its degradation product sulforaphane plays an essential role in anticancer. The fine mapping of sulforaphane metabolism quantitative trait loci (QTLs) in broccoli florets is necessary for future marker-assisted selection strategies. In this study, we utilized a doubled haploid population consisting of 176 lines derived from two inbred lines (86,101 and 90,196) with significant differences in sulforaphane content, coupled with extensive genotypic and phenotypic data from two independent environments. A linkage map consisting of 438 simple sequence repeats markers was constructed, covering a length of 1168.26 cM. A total of 18 QTLs for sulforaphane metabolism in broccoli florets were detected, 10 were detected in 2017, and the other 8 were detected in 2018. The LOD values of all QTLs ranged from 3.06 to 14.47, explaining 1.74-7.03% of the biochemical variation between two years. Finally, 6 QTLs (qSF-C3-1, qSF-C3-2, qSF-C3-3, qSF-C3-5, qSF-C3-6 and qSF-C7) were stably detected in more than one environment, each accounting for 4.54-7.03% of the phenotypic variation explained (PVE) and a total of 30.88-34.86% of PVE. Our study provides new insights into sulforaphane metabolism in broccoli florets and marker-assisted selection breeding in Brassica oleracea crops.

Induced changes in bioactive compounds of broccoli juices after fermented by animal- and plant-derived Pediococcus pentosaceus

To investigate the metabolism of bioactive compounds in broccoli juice fermented by animal- and plant-derived Pediococcus pentosaceus, levels of glucosinolates (GS), sulforaphane, and sulforaphane-nitrile; activity of myrosinase; and profiles of organic acids, vitamins, and amino acids were determined. Three aliphatic GS and four indolyl GS were identified. After fermentation by plant- and animal-derived P. pentosaceus, myrosinase activity, contents of total GS and sulforaphane nitrile, and levels of malic acid, acetic acid, ascorbic acid, and thiamine significantly decreased in pasteurized broccoli juice, whereas levels of sulforaphane, lactic acid, and citric acid significantly increased. Fermentation by plant-derived P. pentosaceus decreased levels of riboflavin and β-carotene and increased total levels of free amino acids, in contrast to the trends observed in broccoli juice after fermentation by animal-derived P. pentosaceus. This study indicates that P. pentosaceus may potentially be used in starter cultures to improve the nutritional and functional properties of fermented foods.

Kinetics of glucosinolate hydrolysis by myrosinase in Brassicaceae tissues: A high-performance liquid chromatography approach

Glucosinolates are a group of secondary metabolites occurring in all the vegetables belonging to the Brassicaceae family. Upon tissue damage, glucosinolates are hydrolyzed by myrosinase to a series of degradation products, including isothiocyanates, which are important for their health-promoting effects in humans. The glucosinolate-myrosinase system has been characterized in several Brassica species, of which white mustard (Sinapis alba) has been studied the most. In this study, a new HPLC-UV assay to evaluate the activities and kinetics of myrosinases in aqueous extracts, which closely represent the physiological conditions of plant tissues, was developed. This method was tested on myrosinases extracted from broccoli and cauliflower inflorescences, employing sinigrin and glucoraphanin as substrates. The results showed a strong inhibition of both enzymes at high substrate concentrations. The main issues related to kinetic analysis on the glucosinolate-myrosinase system were also elucidated.

Thermosonication for the Production of Sulforaphane Rich Broccoli Ingredients

A large proportion of broccoli biomass is lost during primary production, distribution, processing, and consumption. This biomass is rich in polyphenols and glucosinolates and can be used for the production of bioactive rich ingredients for food and nutraceutical applications. This study evaluated thermosonication (TS) (18 kHz, 0.6 W/g, 40–60 °C, 3–7 min) for the pre-treatment of broccoli florets to enhance enzymatic conversion of glucoraphanin into the bioactive sulforaphane. TS significantly increased sulforaphane yield, despite a decrease in myrosinase activity with increasing treatment intensity. The highest sulforaphane yield of ~2.9 times that of untreated broccoli was observed for broccoli thermosonicated for 7 min at 60 °C, which was 15.8% higher than the corresponding yield for thermal processing without sonication (TP) at the same condition. This was accompanied by increase in the residual level of glucoraphanin (~1.8 and 2.3 time respectively after TP and TS at 60 °C for 7 min compared to control samples) indicating that treatment-induced release of bound glucoraphanin from the cell wall matrix and improved accessibility could be at least partially responsible for the enhanced sulforaphane yield. The result indicates the potential of TS for the conversion of broccoli biomass into high sulforaphane broccoli-based ingredients.

The glucosinolates and their bioactive derivatives in Brassica: a review on classification, biosynthesis and content in plant tissues, fate during and after processing, effect on the human organism and interaction with the gut microbiota

The present study is a systematic review of the scientific literature reporting content, composition and biosynthesis of glucosinolates (GLS), and their derivative compounds in Brassica family. An amended classification of brassica species, varieties and their GLS content, organized for the different plant organs and in uniformed concentration measure unit, is here reported for the first time in a harmonized and comparative manner. In the last years, the studies carried out on the effect of processing on vegetables and the potential benefits for human health has increased rapidly and consistently the knowledge on the topic. Therefore, there was the need for an updated revision of the scientific literature of pre- and post-harvest modifications of GLS content, along with the role of gut microbiota in influencing their bioavailability once they are ingested. After analyzing and standardizing over 100 articles and the related data, the highest GLS content in Brassica, was declared in B. nigra (L.) W. D. J. Koch (201.95 ± 53.36 µmol g^-1), followed by B. oleracea Alboglabra group (180.9 ± 70.3 µmol g^-1). The authors also conclude that food processing can influence significantly the final content of GLS, considering the most popular methods: boiling, blanching, steaming, the latter can be considered as the most favorable to preserve highest level of GLS and their deriviatives. Therefore, a mild-processing strategic approach for GLS or their derivatives in food is recommended, in order to minimize the loss of actual bioactive impact. Finally, the human gut microbiota is influenced by Brassica-rich diet and can contribute in certain conditions to the increasing of GLS bioavailability but further studies are needed to assess the actual role of microbiomes in the bioavailability of healthy glucosinolate derivatives.

Simultaneous Analysis of Glucosinolates and Isothiocyanates by Reversed-Phase Ultra-High-Performance Liquid Chromatography-Electron Spray Ionization-Tandem Mass Spectrometry

A new method to simultaneously analyze various glucosinolates (GSLs) and isothiocyanates (ITCs) by reversed-phase ultra-high-performance liquid chromatography-electron spray ionization-tandem mass spectrometry has been developed and validated for 14 GSLs and 15 ITCs. It involved derivatization of ITCs with N-acetyl-l-cysteine (NAC). The limits of detection were 0.4-1.6 μM for GSLs and 0.9-2.6 μM for NAC-ITCs. The analysis of Sinapis alba, Brassica napus, and Brassica juncea extracts spiked with 14 GSLs and 15 ITCs indicated that the method generally had good intraday (≤10% RSD) and interday precisions (≤16% RSD). Recovery of the method was unaffected by the extracts and within 71-110% for GSLs and 66-122% for NAC-ITCs. The method was able to monitor the enzymatic hydrolysis of standard GSLs to ITCs in mixtures. Furthermore, GSLs and ITCs were simultaneously determined in Brassicaceae plant extracts before and after myrosinase treatment. This method can be applied to further investigate the enzymatic conversion of GSLs to ITCs in complex mixtures.

Recent advances in allelopathy for weed control: from knowledge to applications

Allelopathy is the biological phenomenon of chemical interactions between living organisms in the ecosystem, and must be taken into account in addressing pest and weed problems in future sustainable agriculture. Allelopathy is a multidisciplinary science, but in some cases, aspects of its chemistry are overlooked, despite the need for a deep knowledge of the chemical structural characteristics of allelochemicals to facilitate the design of new herbicides. This review is focused on the most important advances in allelopathy, paying particular attention to the design and development of phenolic compounds, terpenoids and alkaloids as herbicides. The isolation of allelochemicals is mainly addressed, but other aspects such as the analysis and activities of derivatives or analogs are also covered. Furthermore, the use of allelopathy in the fight against parasitic plants is included. The past 12 years have been a prolific period for publications on allelopathy. This critical review discusses future research areas in this field and the state of the art is analyzed from the chemist's perspective. © 2019 Society of Chemical Industry.

Methyl jasmonate treated broccoli: Impact on the production of glucosinolates and consumer preferences

Applying methyl jasmonate can mimic the defense response to insect damage in broccoli and enhances the production of glucosinolates, especially inducible indolyl GS-neoglucobrassicin. Previous studies have suggested that glucosinolates and their hydrolysis products are anti-carcinogenic. Therefore, MeJA treatment may increase the nutritional quality of broccoli. However, there are few reports on the sensory evaluation and consumer acceptance of MeJA-treated broccoli. In this study, an untrained consumer panel could not detect any taste differences between steamed MeJA-treated and untreated broccoli, even though the steamed MeJA-treated broccoli contained 50% more glucosinolates than untreated broccoli. The partial least square-regression model suggested that neoglucobrassicin-derived hydrolysis compounds were the major metabolites that determined overall preference for raw MeJA-treated broccoli potentially due to their potential negative sensory qualities. The results imply that MeJA treatment can increase the nutritional quality of broccoli without sacrificing taste in precooked meals or frozen vegetables.

Myrosinase: insights on structural, catalytic, regulatory, and environmental interactions

Glucosinolate-myrosinase is a substrate-enzyme defense mechanism present in Brassica crops. This binary system provides the plant with an efficient system against herbivores and pathogens. For humans, it is well known for its anti-carcinogenic, anti-inflammatory, immunomodulatory, anti-bacterial, cardio-protective, and central nervous system protective activities. Glucosinolate and myrosinase are spatially present in different cells that upon tissue disruption come together and result in the formation of a variety of hydrolysis products with diverse physicochemical and biological properties. The myrosinase-catalyzed reaction starts with cleavage of the thioglucosidic linkage resulting in release of a D-glucose and an unstable thiohydroximate-O-sulfate. The outcome of this thiohydroximate-O-sulfate has been shown to depend on the structure of the glucosinolate side chain, the presence of supplementary proteins known as specifier proteins and/or on the physiochemical condition. Myrosinase was first reported in mustard seed during 1939 as a protein responsible for release of essential oil. Until this date, myrosinases have been characterized from more than 20 species of Brassica, cabbage aphid, and many bacteria residing in the human intestine. All the plant myrosinases are reported to be activated by ascorbic acid while aphid and bacterial myrosinases are found to be either neutral or inhibited. Myrosinase catalyzes hydrolysis of the S-glycosyl bond, O-β glycosyl bond, and O-glycosyl bond. This review summarizes information on myrosinase, an essential component of this binary system, including its structural and molecular properties, mechanism of action, and its regulation and will be beneficial for the research going on the understanding and betterment of the glucosinolate-myrosinase system from an ecological and nutraceutical perspective.